Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
S = [['#'] * (W + 2) for _ in range(H + 2)]
c = 0
for i in range(1, H+1):
    s = list(input())
    S[i] = ['#'] + s + ['#']
    c += s.count('.')

step = [(1, 0), (-1, 0), (0, 1), (0, -1)]
que = deque([(1, 1)])
S[1][1] = 1
while que:
    h, w = que.popleft()
    if (h, w) == (H, W):
        break
    for dh, dw in step:
        nh = h + dh
        nw = w + dw
        if S[nh][nw] != '.':
            continue
        que.append((nh, nw))
        S[nh][nw] = S[h][w] + 1
print(-1 if S[H][W] == '.' else c - S[H][W])